Optical device

ABSTRACT

There is provided an optical device which comprises a fixed barrel, a movable cam ring, and collars and abutments. The movable cam ring is shifted relative to the fixed barrel to move an optical unit, the movable cam ring being fitted to the fixed barrel. Collars and abutments can be engaged with each other when the movable cam ring is in a predetermined positional relationship with respect to the fixed barrel. The collars and abutments preventing the movable cam ring from being disengaged from the fixed barrel and displaced in a direction along an optical axis relative to the fixed barrel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an optical device such as lens barrels used inimage pickup devices, and more particularly to a support mechanism forsupporting the optical device.

2. Prior Art

Conventionally, an image pickup device has been proposed which isprovided with a zoom mechanism having lens barrels composed of a fixedbarrel rigidly fixed to the body of the image pickup device and having acam groove formed in an inner peripheral surface thereof, and a movingcam ring fitted in the cam groove, wherein the moving cam ring is drivenfor rotation by a motor so as to move a zoom lens.

In the image pickup device of this kind, the moving cam ring issupportedly fitted in the cam groove of the fixed barrel only by meansof three followers formed with tapers.

Therefore, when an external force, e.g. an impact, is applied to thelens barrel in an extended position, there is a fear that the moving camring becomes disengaged from the cam groove of the fixed barrel.

One way to solve this problem may be to employ a method of usingfollowers with no tapers for supporting the moving cam ring in the fixedbarrel. This method, however, has the disadvantage that the lens barrelcan be broken, although disengagement of the moving cam ring can beprevented. Further, another problem may arise, that is, the moving camring cannot be centered.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problems, andan object thereof is to provide an optical device which is free fromdisengagement of coupling elements of a coupling mechanism for moving anoptical unit even if an external force, such as an impact, is applied tothe optical device.

To attain the above object, the present invention provides an opticaldevice comprising a first barrel, a second barrel that is shiftedrelative to the first barrel for moving an optical unit, the secondbarrel being fitted to the first barrel, and first and second engagingportions which can be engaged with each other when the second barrel isin a predetermined positional relationship with respect to the firstbarrel, the first and second engaging portions preventing the secondbarrel from being disengaged from the first barrel and displaced in adirection along an optical axis relative to the first barrel.

Preferably, the first barrel comprises a fixed barrel.

More preferably, the second barrel comprises a moving cam ring.

Preferably, the first and second engaging portions comprise protrusionswhich cane be engaged with each other.

Preferably, the first and second engaging portions are provided on thefirst barrel and the second barrel, respectively.

Preferably, the second barrel is brought into the predeterminedpositional relationship with respect to the first barrel, when thesecond barrel is shifted forward relative to the first barrel.

More preferably, when the second barrel is in the predeterminedpositional relationship with respect to the first barrel, the secondengaging portion is positioned in front of the first engaging portion.

Preferably, the optical device comprises a lens barrel.

Preferably, the optical device comprises an image pickup device.

The above and other objects, features, and advantages of the inventionwill become more apparent from the following detailed description takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a lens barrel block of acamera as an image pickup device to which is applied an optical deviceaccording to an embodiment of the present invention;

FIG. 2 is a longitudinal sectional view showing the lens barrel block ina collapsed position;

FIG. 3 is a longitudinal sectional view showing the lens barrel block ina wide-angle position;

FIG. 4 is a longitudinal sectional view showing the lens barrel block ina telephoto position;

FIG. 5 is an exploded perspective view of a shutter unit;

FIG. 6 is a view showing angles of rotation of respective rotors of ashutter and a diaphragm;

FIG. 7 is a perspective view showing a three-group lens barrel and astepping motor;

FIG. 8 is an exploded perspective view of the stepping motor;

FIG. 9 is a view showing cam grooves formed in an inner surface of amoving cam ring;

FIG. 10 is a view showing changes in relative positional relationshipbetween a collar provided on an outer peripheral surface of the movingcam ring and an abutment provided on an inner peripheral surface of afixed barrel;

FIG. 11 is a view, partly cut away, showing a gear train connected to azoom motor;

FIG. 12A is a view showing the arrangement of a device for detecting therotation of the zoom motor;

FIGS. 12B and 12C are timing charts which are useful in explaining amethod of detecting the rotation of the zoom motor, in which;

FIG. 12B is a timing chart showing output waveforms of photointerrupters 54, 55 exhibited when the zoom motor is rotating in onedirection and an output signal from a photo interrupter 48 fordetermining an initial position (zoom reset position); and

FIG. 12C is a timing chart similar to FIG. 12B, showing output waveformsof the photo interrupters 54, 55 exhibited when the zoom motor isrotating in the other or opposite direction and an output signal fromthe photo interrupter 48;

FIG. 13 is a sectional view showing how the lens barrel is connected tothe body of the camera;

FIG. 14 is a view useful in explaining the operation of a finder camplate at an initial stage of a variable power operation;

FIG. 15 is a view useful in explaining the operation of the finder camplate at a middle stage of the variable power operation;

FIG. 16 is a view useful in explaining the operation of the finder camplate at a final stage of the variable power operation;

FIG. 17 is a block diagram showing the arrangement of a control systemof the camera to which is applied the optical device according to theinvention;

FIG. 18 is a flowchart showing the procedure of a control operation ofthe FIG. 17 control system when the power of the camera is turned on;and

FIG. 19 is a flowchart showing the procedure of a control operation ofthe FIG. 17 control system when the power of the camera is turned off.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The present invention will now be described in detail with reference tothe drawings showing an embodiment thereof.

FIG. 1 is an exploded perspective view of a lens barrel block of acamera as an image pickup device to which is applied an optical deviceaccording to an embodiment of the present invention. FIGS. 2 to 4 arelongitudinal sectional views of the lens barrel block, in which FIG. 2shows the lens barrel block in a collapsed position, FIG. 3 shows thelens barrel block in a wide-angle position, and FIG. 4 shows the lensbarrel block in a telephoto position.

In FIG. 1, reference numeral 1 designates a base of a lens barrel unit,which forms a frame structure of the lens barrel unit fixed to a body ofthe camera together with a fixed barrel 2 rigidly screwed onto a frontend of the base 1. Reference numeral 3 designates a first-group lensbarrel that holds lenses 4 and 5. Further, the first-group lens barrel 3has three follower pins 6, which each have a tapered end portion andpress-fitted into an outer peripheral surface of the lens barrel 3, anda cap 7 rigidly bonded to a front surface of the lens barrel 3.

Reference numeral 8 designates a shutter unit that holds lenses 9, 10,11, and 12. FIG. 5 is an exploded perspective view of the shutter unit8. As shown in the figure, a diaphragm bottom board 13 has an outerperiphery thereof integrally formed with two followers 13 a each havinga tapered portion at a distal end thereof, and one movable follower 81that is movable in a direction orthogonal to the optical axis of thelens barrel unit. The above three followers are arranged atcircumferentially equal intervals on the outer periphery of thediaphragm bottom board 13. The movable follower 81 is urged radiallyoutwardly of the diaphragm bottom board 13 by a compression spring 80(FIG. 3). This makes it possible to prevent the centers of the lenses 9,10, 11, and 12 held by the shutter unit 8 from deviating from theoptical axis, thereby preventing degradation of photographing accuracyof the camera.

Reference numerals 82 and 83 designate coils wound around respectivebobbins. When the coils 82 and 83 are energized, respective magneticfluxes generated by the energization cause, via yokes 84 and 85,magnetic torque to be generated in magnets 87 and 89 to therebypivotally move arms 86 and 88 integrally formed with the magnets 87 and89. The angles of pivotal movement of the arms 86 and 88 are limited byopenings 13 b and 13 c formed in the diaphragm bottom board 13, suchthat the arms 86 and 88 can be moved within movable ranges shown in FIG.6. In other words, respective arm portions 86 a and 88 a of the arms 86and 88 abut on opposite ends of the respective openings 13 b and 13 c tostop the respective pivotal movements of the arms 86 and 88.

When the pivotal movements of the arms 86 and 88 are stopped, the arms86 and 88 are halted at positions where the magnets 87 and 89magnetically attract the yokes 84 and 85 according to their polarities.Hence, the arms 86 and 88 are held in the halted state even after theenergization of the coils 82 and 83 is stopped. Further, also when thearms 86, 88 are halted after the inverted pivotal movements of the arms86 and 88 which cause the respective arm portions 86 a and 88 a thereofto abut on the ends of the openings 13 b and 13 c opposite to theabove-mentioned ends, the magnetically attracting forces are similarlyapplied to the yokes 84 and 85 at the respective halted positions of thearms 86 and 88. This makes it possible to hold the arms 86 and 88 in thehalted state without currents flowing through the coils 82 and 83.

Reference numeral 90 designates a diaphragm blade which has a slot 90 awith the arm portion 86 a of the arm 86 inserted therein. Further, thediaphragm blade 90 has a hole 90 b rotatably fitted on a pivot 13 d ofthe diaphragm bottom board 13. The diaphragm blade 90 has an aperturewhich is circular in shape, and further has an ND filter 91 attachedthereto to thereby limit the amount of light. This is because in ahigh-density image pickup device of a recent digital camera, when thediameter of the aperture is small, an adverse influence of diffraction,which can degrade the quality of a formed image, cannot be neglected,and therefore, the ND filter is provided to limit the amount of lightwithout degrading the quality of the formed image.

Reference numerals 92 and 93 designate shutter blades. The shutterblades 92 and 93 have holes 92 b and 93 b, respectively, which arerotatably fitted on respective pivots 13 e and 13 f provided on thediaphragm bottom board 13. The arm portion 88 a formed on the arm 88 isinserted into slots 92 a and 93 a formed through the respective shutterblades 92 and 93.

Reference numeral 94 designates a cap for fixedly holding the coils 82and 83, and the yokes 84 and 85, and rotatably holding the arm 86 (withthe magnet 87) and the arm 88 (with the magnet 89) between itself andthe diaphragm bottom board 13. Reference numeral 96 designates a casingfor preventing the diaphragm blade 90 from being detached from theshutter unit 8. Reference numeral 95 designates a sheet for preventinginterference between the diaphragm blade 90 and the shutter blades 92and 93. Further, the sheet 95 has an open aperture 95 a formed through acentral portion thereof, which is open when the diaphragm blade 90 isretreated.

In FIG. 1, reference numeral 14 designates a third-group lens barrelthat holds a lens 15. The third-group lens barrel 14 is guided by aguide bar 16 and a guide shaft 1 a provided on the base 1. Further, asshown in FIG. 7, the lens barrel 14 has its position in an axialdirection, i.e. a direction along the optical axis limited by a nut 17formed with an internal or female thread and held between arm portionsof the lens barrel 14, and is biased by a tension spring 18 in adirection in which the lens barrel 14 is withdrawn. The nut 17 has aslit 17 a formed therein, in which a projection 14 a of the lens barrel14 is fitted, whereby the rotation of the nut 17 is restrained by thelens barrel 14.

In FIG. 3, reference numeral 19 designates a screw shaft integrallyformed with a magnet 20, which has a trailing threaded portion matingwith the female thread of the nut 17.

In FIG. 1, reference numeral 21 designates a stepping motor for drivingthe third-group lens barrel 14. As shown in FIG. 8, the stepping motor21 includes a yoke plate 25 to which are attached two sets ofcomponents, i.e. a pair of yokes 22, 23 arranged in a manner opposed toeach other in the axial direction, and coils 24, 24 wound aroundrespective bobbins and associated with the respective yokes 22, 23, suchthat the two sets are opposed to each other with the magnet 20positioned therebetween. The stepping motor 21 is rigidly fixed to thebase 1 by screwing the yoke plate 25 onto the base 1.

In FIG. 1, reference numeral 26 designates a photo interrupter rigidlyfixed to the base 1. The photo interrupter 26 is arranged at a positionwhere a slit plate 14 b integrally fixed to the third-group lens barrel14 is permitted to enter or retreat from a slit of the photo interrupter26. Reference numeral 28 designates a cap rigidly fixed to the base 1,to which is fixed a distal end side of the guide bar 16, to rotatablyhold the screw shaft 19.

In FIG. 1, reference numeral 29 designates an image pickup device whichis rigidly bonded to and held by a holding plate 30 rigidly screwed ontothe base 1. Reference numeral 31 designates a flexible base board towhich the image pickup device 29 is soldered. The image pickup device 29photoelectrically converts an input optical image to an image signalindicative of the input optical image, and supplies the image signal toa signal processing circuit, referred to hereinafter. Reference numerals32 and 33 designate a dustproof rubber and an LPF (Low Pass Filter),respectively, both of which are rigidly fixed to the base 1 by bondingor the like.

Referring to FIG. 10, the fixed barrel 2 has an inner peripheral surfacethereof formed with a cam groove 2 a, in which is engaged a metalfollower pin 27 press-fitted in the moving cam ring 34. Thus, the movingcam ring 34 is rotated along the cam groove 2 a, whereby the moving camring 34 is moved in the direction along the optical axis.

The moving cam ring 34 has an outer periphery thereof formed with gearteeth 34 a. As shown in FIG. 11, a zoom motor 35 has a rotational shaftthereof connected to the gear teeth 34 a via a reduction gear traincomprised of reduction gears 36 to 41. The torque of the zoom motor 35is transmitted to the gear teeth 34 a through the reduction gears 36 to41 such that the rotational speed of the zoom motor 35 is progressivelyreduced, whereby the moving cam ring 34 is rotatively driven to move inthe direction along the optical axis. Referring to FIG. 12A, thereduction gear 36 has three blades 36 a mounted thereon for detectingthe rotation of the zoom motor 35, and photo interrupters 54 and 55 arearranged at an angle of 150 degrees such that the three blades 36 a canblock slits of the photo interrupters 54 and 55. Further, the reductiongear 41 and a shaft 43 thereof are made of metal.

As shown in FIG. 13, nickel-plated gaskets 45 are affixed to the innersurface of a casing 44 of the body of the pickup device for impartingresilience to the assembly of the casing 44 and components attachedthereto via the gaskets 45. Therefore, when the lens barrels areassembled with the body of the pickup device, the lens barrels arebought into intimate contact with the body of the pickup device.Further, the first-group lens barrel 3 and the moving cam ring 34 aremolded from a mixture of molding resin and carbon fiber.

In FIG. 1, reference numeral 46 designates a finder cam plate. As shownin FIGS. 3 and 4, the finder cam plate 46 has an outer surface thereofformed with taper cam grooves 46 b and 46 c for driving a finder lensfor zooming operation. The inner surface of the finder cam plate 46 isformed with a guide key 46 a fitted in a groove 2 d formed in the fixedbarrel 2 such that the finder cam plate 46 can be rotated along theouter periphery of the fixed barrel 2. Reference numeral 47 designates atension spring with one end thereof rigidly fixed to the finder camplate 46 and the other end thereof rigidly fixed to the fixed barrel 2such that the finder cam plate 46 is normally biased toward thewide-angle position.

A straight advance guide barrel 42 shown in FIG. 1 is rotatably fittedin the moving cam ring 34. The straight advance guide barrel 42 includesa projection 42 e which is fitted in a groove 2 c (see FIG. 10) formedin the fixed barrel 2 such that the straight advance guide barrel 42 isprevented from rotating with respect to the fixed barrel 2. Further, thestraight advance guide barrel 42 has three projections 42 f formed on afront end thereof and fitted in a groove 34 e (see FIG. 9) formed in theinner surface of the moving cam ring 34.

With this construction, the straight advance guide barrel 42 and themoving cam ring 34 are moved in unison with each other in the directionalong the optical axis while they can rotate relative to each other. Asshown in FIG. 9, the metal follower pins 6 provided on the first-grouplens barrel 3 are engaged with cam grooves 34 b formed in the moving camring 34 while straight movement grooves 42 a formed in the straightadvance guide barrel 42 are engaged with straight moving pins 3 aprovided on the first-group lens barrel 3. The straight movement grooves42 a and the straight moving pins 3 a cooperate to restrain rotation ofthe first-group lens barrel 3, and cause the first-group lens barrel 3to be moved in the direction along the optical axis as the moving camring 34 is rotated. Similarly, the shutter unit 8 is engaged with a camgroove 34 c formed in the moving cam ring 34 and a straight movementgroove 42 b formed in the straight advance guide barrel 42, whereby thestraight movement groove 42 b restrains rotation of the shutter unit 8.Thus, when the moving cam ring 34 is rotated, the shutter unit 8 ismoved along the cam groove 34 c in the direction along the optical axis.

The moving cam ring 34 has a collar means 34 d provided on an outerperipheral surface thereof, while the fixed barrel 2 has an abutmentmeans 2 b provided on an inner peripheral surface thereof at a locationwhere the abutment means 2 b can be brought into contact with the collarmeans 34 d. The collar means 34 d is comprised of four elongated members(collars) which circumferentially extend on the outer peripheral surfaceof the moving cam ring 34 at equal intervals. The abutment means 2 b iscomprised of two elongated members (abutments) each of which is longerthan the elongated members of the collar means 34 d, and whichcircumferentially extend on the inner peripheral surface of the fixedbarrel 2 at diametrically opposite locations. As shown in FIGS. 2 and10, when the moving cam ring 34 is rotated to shift from the collapsedposition to the wide-angle position, that is, when a picture is nottaken, the collar means 34 d is positioned on the image surface sidewith respect to the abutment means 2 b on the fixed barrel 2. On theother hand, as shown in FIGS. 3, 4 and 10, when the moving cam ring 34is positioned in a range from the wide-angle position to the telephotoposition in which a picture can be taken, that is, when a picture istaken, the collar means 34 d is always positioned on the object sidewith respect to the abutment means 2 b, where the collar means 34 d canabut on the abutment means 2 b.

With this construction, if an external force acts on the first-grouplens barrel 3 and the moving cam ring 34 when the lens barrel is in aposition where a picture can be taken, the external force is absorbed bythe abutment means 2 b provided on the inner peripheral surface of thefixed barrel 2, whereby the follower pin 27 press-fitted in the movingcam ring 34 can be prevented from becoming disengaged from the camgroove 2 a formed in the fixed barrel 2, thereby preventing the lensbarrel from being damaged.

It should be noted that as shown in FIG. 1, the collar means 34 d andthe abutment means 2 b are elongated circumferentially of the moving camring 34 and the fixed barrel 2, with the longer sides of the collarmeans 34 d and the abutment means 2 b being parallel with each other.Therefore, when the collar means 34 d abuts on the abutment means 2 b,the longer sides of these means are in contact with each other over thewhole and a major part of lengths thereof, which contributes toenhancement of the effects described above.

Further, as shown in FIG. 13, the third-group lens barrel 14, the movingcam ring 34, the reduction gear 41 of the reduction gear train, theshaft 43, and the gaskets 45 are electrically connected to the casing 44which is grounded to an electric circuit, so that even if staticelectricity is generated in the camera body, the static electricity doesnot adversely affect the electric circuit.

FIG. 17 is a block diagram schematically showing the arrangement of acontrol system of the camera according to the embodiment. An imagesignal output from the image pickup device 29 is subjected topredetermined processes, such as color conversion and gamma correction,by an image processing circuit 61, and then stored in a memory 62, suchas a card medium.

A control section 60 carries out overall control of the camera. Morespecifically, the control section 60 controls driving of the steppingmotor 21, the shutter unit 8, and the zoom motor 35 while monitoringoutputs from the photo interrupters 54 and 55 within the lens barrel,the photo interrupter 26, and a photo interrupter 48 for detecting azoom reset, to thereby carry out distance measurement control, exposurecontrol, and zooming control. Further, the control section 60 alsocontrols the above-mentioned signal processing and the operation of thememory 62.

Reference numeral 64 designates an electrically erasable/recordablenonvolatile memory which is formed by an EEPROM, for instance. Referencenumeral 63 designates an electrically erasable/recordable volatilememory for storing variables used in controlling the camera. The memory63 is formed e.g. by a SRAM (static RAM).

Next, operations carried out when the power is turned on and when it isturned off will be described with reference to respective flowchartsshown in FIGS. 18 and 19.

Referring to FIG. 18, when a power switch 65 (see FIG. 7) of the camerais turned on at a step S1, it is determined at a step S2 whether or notthe lens barrel is in the collapsed position. If it is determined thatthe lens barrel is in the collapsed position, the zoom motor 35 isdriven for rotation to thereby extend the lens barrel by a predeterminedamount at a step S3.

At this time, as described hereinbefore, the torque of the zoom motor 35is transmitted to the gear teeth 34 a formed on the moving cam ring 34through the reduction gear train of the reduction gears 36 to 41. (seeFIG. 11). Then, the moving cam ring 34 is rotated clockwise as viewed inFIG. 11 and a lens barrier 49 incorporated in the first-group lensbarrel 3 (see FIG. 3) starts to open.

When the moving cam ring 34 is further rotated, normally, the lensbarrel is extended to an initial position. This initial position of thelens barrel is detected such that a light shielding plate 42 c arrangedon the bottom of the straight advance guide barrel 42 blocks lightincident to the photo interrupter 48 bonded to the base 1 to therebycause switching of an output signal from the photo interrupter 48.Therefore, it is determined at a step S4 whether or not the outputsignal from the photo interrupter 48 has been switched within apredetermined time period. If the output signal from the photointerrupter 48 has not been switched within the predetermined timeperiod, it means that the lens barrel has not been properly extendedfrom the collapsed position into the initial position, and therefore afirst error handling process is carried out at a step S9.

As described hereinabove, the reduction gear 36 of the reduction geartrain has the three blades 36 a arranged thereon. The passing of theseblades 36 a is detected by the photo interrupters 54 and 55, whereby therotation of the zoom motor 35 is converted into pulse waves, and thepulse waves are counted to detect a number of rotations of the zoommotor 35. The number of rotations of the zoom motor 35 is counted withreference to the above-mentioned initial position of the lens barrel,and numbers of rotations corresponding to the respective zoom positionsof the lens barrel, i.e. the wide-angle position, a middle position, andthe telephoto position are stored in the nonvolatile memory 64.

To move or extend the lens barrel into a desired one of the zoompositions with accuracy, it is necessary to reliably count the number ofrotations of the zoom motor 35 up to a corresponding one of the numbersof rotations stored in the nonvolatile memory 64. However, the rotationof the zoom motor 35 cannot be stopped instantly only by stoppingenergization of the zoom motor 35, due to inertia of a rotor of the zoommotor itself and the gears associated therewith, which sometimes causesexcessive rotation of the zoom motor 35. To overcome this problem, acurrent is caused to flow to the zoom motor 35 so as to drive the samein a direction of reverse rotation to cause the zoom motor 35 to bestopped instantly. Therefore, unless the direction of rotation of thezoom motor 35 is taken into consideration, the number of rotations ofthe zoom motor 35 cannot be counted accurately.

In the present embodiment, the two photo interrupters 54 and 55 areemployed as means for detecting the direction of rotation of the zoommotor 35. FIGS. 12B and 12C show output waveforms of the photointerrupters 54 and 55 and output signals from the photo interrupter 48that determines the initial position (zoom reset position), FIG. 12Bshowing a case where the zoom motor 35 is rotating in one direction, andFIG. 2C a case where the zoom motor 35 is rotating in the other orreverse direction. When the zoom motor 35 is rotating clockwise (CW) asviewed in FIG. 11, the waveform of the photo interrupter 55 precedes thewaveform of the photo interrupter 54 by ¼ cycles, as shown in FIG. 12B,whereas when the zoom motor 35 is rotating counterclockwise (CCW) asviewed in FIG. 11, the waveform of the photo interrupter 55 lags behindthat of the photo interrupter 54 by ¼ cycles, as shown in FIG. 12C.

Thus, the relationship in output timing between the photo interrupters54 and 55 changes depending on the direction of rotation of the zoommotor 35. Therefore, by detecting this change, the direction of rotationof the zoom motor 35 can be detected to thereby count the number ofrotations of the motor with accuracy.

After the lens barrel has thus been driven into the initial position,the lens barrel is further moved into an extreme wide-angle end positionwhere a picture can be taken (wide-angle end position), at a step S5.During this movement of the lens barrel, as shown in FIG. 14, the findercam plate 46 remains stationary with a guide end 46 e thereof being inabutment with a groove end 2 f of the fixed barrel 2.

Referring to FIG. 15, the finder cam plate 46 and a projection 34 fprovided on the moving cam ring 34 start to be brought into contact witheach other immediately before the lens barrel reaches the wide-angleposition. Thereafter, as shown in FIG. 16, as the lens barrel is movedfrom the wide-angle position to the telephoto position, the finder camplate 46 is moved together with the moving cam ring 34 while beingbiased toward the wide-angle position by the tension spring 47, wherebya variater lens and a compensator lens of an optical finder, not shown,are actuated for a power varying operation of the finder in a mannersuited to the focal length of the image pickup optical system.

After the lens barrel has been moved into the wide-angle position, thethird-group lens barrel 14 which has been in a retreated position ismoved to its initial position by the stepping motor 21 at a step S6.More specifically, when the stepping motor 21 is driven, the screw shaft19 is rotated via the magnet 20. Then, the nut 17, the rotation of whichis prevented by the projection 14 a of the third-group lens barrel 14,is moved in the direction along the optical axis, and the third-grouplens barrel 14 is also moved in the direction along the optical axis ina manner following the nut 17 to adjust the focus. In this process,normally, the slit plate 14 b enters or retreats from the slit of thephoto interrupter 26 within the stroke of operation of the third-grouplens barrel 14, and switches the output of the photo interrupter 26,whereby the count of a counter for detecting the number of steps of thestepping motor 21 is reset to complete the movement of the third-grouplens barrel 14 into the initial position.

Therefore, it is determined at a step S7 whether or not the outputsignal from the photo interrupter 26 has been switched within apredetermined time period. If the output signal from the photointerrupter 26 has not been switched, it is determined that some problemhas arisen, and a second error handling process is carried out at a stepS10.

On the other hand, if the output signal from the photo interrupter 26has been switched within the predetermined time period, the steppingmotor 21 is further driven to thereby move the third-group lens barrel14 into a standby position on the wide-angle side. Further, controloperations, including control of the diaphragm aperture size, and whitebalance adjustment, are carried out according to the lightness of anobject or the like to complete the preparations for taking a picture ofthe object, at a step S8.

As described hereinabove, when the camera has thus become ready fortaking a picture, the operator can operate a zoom lever, not shown, to atelephoto side, and release the same at a desired zoom position, tothereby set the variable power ratio as desired.

When the operator turns off the power switch 65 at a step S11 shown inFIG. 19, the third-group lens barrel 14 is moved into a standby positionon a collapsed position side by the stepping motor 21 at a step S12. Inthis case, if the third-group lens barrel 14 is properly moved into thestandby position on the collapsed position side, the output signal fromthe zoom-resetting photo interrupter 48 is switched, and hence it isdetermined at a step S13 whether or not switching in the output signalfrom the photo interrupter 48 has been detected. If the switching of theoutput signal from the photo interrupter 48 has not been detected, it isdetermined that some problem has arisen, and the first error handlingprocess is carried out at a step S16.

On the other hand, if the switching of the output signal from the photointerrupter 48 has been detected, the lens barrel is moved into thecollapsed position at a step S14, and then an electrical terminationprocess is carried out, followed by turning off the power at a step S15.

The present invention is not necessarily limited to the above describedembodiment, but various changes and modifications may be made withoutdeparting from the scope of the appended claims.

For example, the present invention may be applied to a construction thatin the above embodiment, the fixed barrel 2 is replaced by a movablebarrel.

Still further, the present invention may be applied to a constructionthat in the above embodiment, the coupling means between the fixedbarrel 2 and the moving cam ring 34 is also applied to that between thecam ring and the lens unit.

1. An image pickup device comprising: a lens barrel unit including afirst barrel having a cam groove formed in an inner peripheral surfacethereof, and a second barrel, said first and second barrels beingshifted relative to each other from a collapsed position in a directionalong an optical axis and into a range from a wide-angle position to atelephoto position in which a picture can be taken; said second barrelbeing engaged with said cam groove of said first barrel and beingmovable toward an object with respect to said first barrel; said secondbarrel having a first projection formed thereon and engaged with saidcam groove; said second barrel having a second projection formed thereonat a position different from a position in which said first projectionis formed; and said first barrel having a third projection formedthereon, for engagement with said second projection, said thirdprojection extending in the range from the wide-angle position to thetelephoto position, wherein: said second projection is positioned on aside toward the object with respect to said third projection when saidlens barrel unit is in the range from the wide-angle position to thetelephoto position; and said second projection abuts on said thirdprojection when an external force acts on said second barrel from theside toward the object.
 2. An image pickup device according to claim 1,wherein said second projection and said third projection are elongatedcircumferentially of said second barrel and said first barrel such thatlonger sides of said second projection and said third projection areparallel with each other.
 3. An image pickup device according to claim1, wherein said second projection is positioned on a side toward animage surface of the image pickup device with respect to said thirdprojection when said lens barrel unit is in a range from the collapsedposition to the wide-angle position in which a picture is not taken. 4.An image pickup device according to claim 1, wherein said thirdprojection is positioned on the side toward the object with respect tosaid second projection when said lens barrel unit is in the collapsedposition.
 5. An image pickup device comprising: a lens barrel unitincluding a first barrel having a cam groove formed in an innerperipheral surface thereof, and a second barrel engaged with said camgroove of said first barrel and being movable to a side toward an objectwith respect to said first barrel; said second barrel having a firstprojection formed thereon and engaged with said cam groove; said secondbarrel having a second projection formed thereon at a position differentfrom a position in which said first projection is formed, said secondprojection being elongated circumferentially of said second barrel; andsaid first barrel having a third projection formed thereon, forengagement with said second projection, said third projection beingelongated circumferentially of said first barrel such that longer sidesof said second projection and said third projection are parallel witheach other, wherein said third projection is positioned on the sidetoward the object with respect to said second projection when said lensbarrel unit is in the collapsed position, and said second projection ispositioned on the side toward the object with respect to said thirdprojection when said lens barrel unit is in the range from thewide-angle position to the telephoto position.
 6. An image pickup deviceaccording to claim 5, wherein said first barrel is a fixed barrel.
 7. Animage pickup device according to claim 5, wherein said second barrel isa moving cam ring.
 8. An image pickup device comprising: a lens barrelunit including a first barrel having a cam groove formed in an innerperipheral surface thereof, and a second barrel, said first and secondbarrels being shifted relative to each other from a collapsed positionin a direction along an optical axis and into a range in which a picturecan be taken; said second barrel being engaged with said cam groove ofsaid first barrel and being movable toward an object with respect tosaid first barrel; said second barrel having a first projection formedthereon and engaged with said cam groove; said second barrel having asecond projection formed thereon at a position different from a positionin which said first projection is formed; and said first barrel having athird projection formed thereon, for engagement with said secondprojection, said second projection being positioned on a side toward anobject with respect to said third projection; wherein when an externalforce acts on said second barrel the side toward the object when saidlens barrel unit is in a range in which a picture can be taken, saidsecond projection is acted upon by the external force into abutment withsaid third projection to absorb the external force.
 9. An image pickupdevice according to claim 8, wherein said first barrel is a fixedbarrel.
 10. An image pickup device according to claim 8, wherein saidsecond barrel is a moving cam ring.
 11. An image pickup device accordingto claim 8, wherein said third projection is positioned on the sidetoward the object with respect to said second projection when said lensbarrel unit is in the collapsed position.